Dehydrator



March 6, 1945. H. w. WOODWA-RD 2,371,095

DEHYDRATOR Filed June 24, 1945 4 Sheets-Sheet l r L A g u 13 7 17 F g Imeziz-- 4 7 gm MOJS'MOJwarJL March 6, 1945. w WOODWARD 2,371,095

DEHYDRATOR Filed June 24, 1943 4 Sheets-Sheet 2 March 6, 1945. w WQODWARD 2,371,095

DEHYDRATOR Filed June 24, 1943 4 Sheets-Sheet 3 March 6, 1945. H.W. WOODWARD DEHYDRATOR 4 Sheets-Shet 4 Filed June 24, 1945 Patented Mar. 6, 1945 DEHYDRATOR Hiram W. Woodward, Baltimore, Md., assig'nor of one-half to Strasburger & Siegel, Baltimore,

,Md., a partnership comprising Le Roy V.

Strasburger and Maurice Siegel Application June 24, 1943, Serial No. 492,104

2 Claims. c1; s r-174) This invention relates to drying or dehydrating apparatus, and more particularly to apparatus for drying or dehydrating foodstuffs such as, to example, fruit, vegetables, and the "like.

Heretofore, numerous attempts have been made to produce adequateand efiiclent apparatus for dehydrating foods. Ihese attempts, for the most art, have consisted 'of dehydrators or driers wherein the drying medium is passed over and/or beneath thesurface of alquantity of food to be dried which has been placed on screens or solid or perforated trays. v

In such dehydrators, in which the drying in dium is passed over. or beneath the surface of a quantity of food,,nt only in the majority of cases must the tray load be extremely light, thus materially limiting the capacity of the.,drier, but passage of the drying medium over or beneath the surface of the food produces an extremely non-uniform drying action because the J drying medium does notreadily penetrate to and contact the food below the surface strata of the mass with the result that the food at the surface is dried much more rapidly than the remainder of the food'and, in many cases, the

sub-surface food is not dried or dehydrated to the degree desired.

On thev other hand, the comparatively few food dehydrators heretoforeattempted. of the type wherein the drying medium is passed entirely through a body or mass of the food being treated have been of the horizontally moving conveyor or screen type in which the food to be dehydrated is deposited onto the moving ,con-

veyor or screen and as it travels along, asuite tionate decrease in the temperature drop between the entering and leaving =dryin'g medlum with a consequent decrease uin 'the' amount of moisture absorbed per pound of the medium passing through the food. a 1

Secondly, the gradually increasing" rate-of flow-resulting from the decreasingre'sistance to flow as drying of the food progresses, produces "a tendency for the drying medium tofollow-the path of least resistance and create-an unbalance in the amount of flow as between theinb tially more moist and drier portions of the food along the length of the conveyor so that', in the absence of adequate control of the drying medium, the greater volume thereofwill pass through the drier, less dense zones ofithe food-tothe exclusion of the more moist andmore dense portionsthereof at the beginnin *of them. 4

Thirdly, high first cost of initial:equipment. With the foregoing in mind, the. principal object of the present invention isto: provide a novel drier or, dehydrator for lfoodstufis of the so-called blow-through type whereinthe resistance to passage of the drying medium offered by the food may. be maintained substantially vconpassage of the drying medium is effected'by 1nable drying medium, usually warm air, is passed upwardly and/or downwardly through the conveyor and through the mass of food carried thereby.

.' Several dimculties and objections are presented by such dehydrators. In the first place, as travel of the conveyor and its load of food progress and the food becomes increasingly dry, both the volcreasing the length or path ,of travel through the food as drying thereof progresses witha conse:

'quent decrease in the rate of moisture diffusion.

Another object of the invention is to provide a food dehydrator as described wherein'length or path of travel of thedrying mediumthrough the food may be increased uniformly and-gradually, and at the desired rate, as drying progresses as distinguished from abrupt changes of the length of air travel between successive stages "or steps.

Another object of the invention isto provide a food dehydrator 0r drier of the character set a given drying procedure and/or the kind or type of food undergoing dehydration. I

A still further object is to provide a dehydrator of the type described wherein the food moves relative to the screen, tray or the like, thereby eliminating the possibility of tray burn.

A further object of the invention is to provide a food dehydrator of. the stated character where in a maximum drop intemperature'is afiorde'd between the entering and leaving drying medium in each stage or section of the dehydrator thereby providing a dehydrator which is character: ized by maximum efficiency and economy in operation and use.

A further object of the invention is 'to 'provide a food dehydrator of the character set;fo rt h wherein the food being dried is fed-and flows entirely by gravity therebyeliminatinggto as: great or-parallel; and. in such arrangementsone or more I of the componentnnits :may be operated from common pressure and/or :exhaust chambers as desired.

.Stilla furtherrobjecto'f the. present invention lsto. provide 'a dehydrator-oridrier of. the stated character-xwh ch:embodieswieatures of construc 110111: and arrangement permitting of its ready adaptation; andnseinrconjunctiorr with. pre-drying equipmentof .texistingwor other'types, and whichmay; be incorporated or inserted at'any predetermined 'location in the drying cycle of existing dehydration-equipment and installations. Thesesand other objects of'the invention and the various: features and: details of. theyconstruc-j tion and arrangement; thereof a are hereinafter fully.set -fortlnand described; and ,shown in the accompanying-drawings,iin which:

- Figure 1.;is ia-sectional.View vertically through a dehydrator made according to thepresent'invention. 1 '.Figurezzisaviewiinsection taken on line 2-2, Figure 1.- I I Figure 3 is. an enlarged-fragmentary view of the :disclosure in Figure 1 illustrating certain structural features anddetaiis of the dehydrator.

Figure 4 1s asectionalview vertically through aiimultiple or seriesform-of dehydrator made according. to thepresentinvention.

Figure':5 is a: sectional view vertically through another; form or arrangement of multiple-series dehydrator embodying the invention. Figure. 6 is a .view inperspectiveoi the dehy-, drator shown in Figure illustrating -.one ar-j rangement of the various input and take off ducts for the dryingairiand IFigure "'7 is. adiagramrnatic. sectional. plan view illustrating a modified air duct and chamber arrangement affording complete flexibility and control of the direction ofiflow of the drying air. Referring now' to the 'drawingaand more particularly to Figure 1 thereof, a dehydrator embodying the'present invention'comprises essentially apair'of screen OIPGl'fOIELIJBd plate members I and 2, respectively, arranged'in generally upstanding =space'dapart relation and disposed more closely-spaced relation at the (top than at the: bottom'tlie'reof to provide a generally vertlcally extending path of travel for the food to be dehydrated which gradually increases in width downwardly. 7

Opening to and in register with the upper end or inlet to the space between the screens or plates I and 2 is a suitable hopper 3 for receiving the o d to b ehyd d andfeed ng it uniformly andtby' gravity downwardly; between-"said screens or plates, and depending 'angularly fromthe bot- .tom or outlet end of the path of food travel de- -fined by the said screens or plates I and 2 a suitable discharge chute or the like 4 may be provided. I I iIn accordance-with the invention, at opposite 'sides'of the screens or plates I and 2, and out- .wardly'thereof', there is provided, respectively, an input chamber (higher pressure) and an exhaust chamber (lower'pressure) for the drying medium. In the embodiment of the invention illustrated in'Figure 1, the input chamber is designated by thev reference 1 numeral 5 .zandzisi disposed at .the outerzsidex of thescreenwor :Lplate F Izwhile :the ex-e haustv chamber is; designated I .6 and disposed 1 at the outensid'e .of the othersrscreen :or plate 42.

In the plane. of the screens I. and 2,- theseohambers 5. and 6 haVeIan/Jarea and ..confi,guration substantially'equal to the-surface area of said screens I and the 'latter iorm or constitute .the inner ,walls of said: chambers" which, in addition, are .;prov idedxwith top-rand bottom walls 1,8, 9 and I0, respectively,::as well asaouter side walls (not shown). The chambersfiaandifi additionally are defined by end walls: I I and. II which extend continuouslyacross the drier or dehydrator and close :or .wall-ofi -:v the endopenings between the two; screens .or plates .I and 2,. as shown in Fignre...2, thereby :confining the food 'to a path of travel between said. screens. Suitable portsor openings, ofrcoursaare provided inone wall of the chamber -5 for admitting the: drying medium theretoanda suitable exhaust-port or opening is" provided in the chamber fi. I I a v #In operation, therefore, the drying medium, which usually is air at: predetermined temperature and humidity,.is admitted under-- apredetermined static pressure to the chamber 5 from which it passes through the screen'onperforate plate'I,=entirelythroughthe column of food F travelling downwardly between thescreens or plates l and 'Z, and then through the other screen or plate 2 into the chamber -6 from which itis exhausted either-to the atmosphere and/or -to be reheated and returned to the chamber Bunder pressurefor recirculation or-passaegthrough the food F as aforesaid. In cases Where the air isreci-rculated, the desired condition (if-absolute humidity may be obtained through the use ofsuitable dampers for regulating-the amount of air recirculated and the amount of make-,up air.

"Now, as previously stated, a 'feature of "the present "invention contemplates "a substantially uniform resistance to air flow throughthe'column of-foodthroughout the extent:of"the' path ofi'low thereof through'thedehydrator, "and the. accomplishment 'of this 'resu'lts-by' gradually increasing the length of the pathof-travel of 'the airthrough the food as drying thereoi'progresses in the course of passage of-themed-downwardly between the screens or plates I andZ Gf -the dehydrator, or, in other words, by gradually increasing the width or thickness of the column of food as it-passes downwardly I between saidscreens 'er I plates. I In 'this-connection,'-it is pointed eii-t that'the rate or gradient of this gradual increase in the width or tliickness. or the -mass or food saw wardly between the screens or plates that maybe necessary to provide a resistance to air flow adjacent the discharge outlet which is commensurate or comparabletothair flow resistance at the inlet where the food, although the thickness or width of the food mass is narrower, is substantially more moist providing' a greater resistance to air flow per unit of-width or thickness than at theoutlet where the food is substantially drier, of course, is dependent upon the kind and type of food to'be dehydrated since difl'erent kinds and types of foodstuffs present different characteristics in respect to the rate that they will flow through the dehydrator and also in respect to'their densityand the rate of moisture absorption or drying thereof, factors which have a controlling eifect upon the resistance to air flow for a given thickness or width ofa mass of a given food. I

' Accordingly, provisionis made in the dehydrator for adjusting'the screens or plates I and 2 relative to each other at either orboththe inlet and outlet ends of the dehydrator to vary the spacing between said screens or plates and/or the relative angular disposition thereof to regulate the gradient or rate at which the width or thickness of the food column increases as it pro gresses downwardly through the dehydrator.

This may be accomplished by any suitable construction and, as an illustrative example of one suitable arrangement, each of the screens or plates I and 2 may be provided at their upper and lower edges with laterally outward extending flanges or portionsI3, I4, I5, I6, respectively, arranged so that the upper edge flanges I3 and I5 thereof underlie the top wall portions I and 9 of the adjacent air chambers 5 and 6 and their lower edge flanges I4 and I6 overlie the bottom wall portions'8 and I'll of said chambers;

As exemplified more particularly in Figure 3 of the drawings, each of the flanges may be releasably secured to the adjacent chamber wall portion by means of a suitable wing nut and bolt or the like I1 which extend through suitable slots I8 provided in said flanges to permit the screens or plates I and 2 selectively to be moved relative to each other and'the top-and bottom walls of the chambers upon loosening of the appropriate wing nuts and bolts I1. g I v In the dehydrator shown in Figure 1 of'the drawings wherein single air chambers are provided at opposite outer sides of the screens or plates I and 2, operation of the dehydrator is usually limited to the passage through the dehydrator of air in one direction only and ata uniform predetermined temperature and static pressure, although the direction of air may be changed as desired and, of course, the temperature, pressure and humidity of the drying air required for any given product is controlled by regulation of the heaters and the make-up air through the usualjdampers, fan; etc. On the other hand, in some adaptations of the dehydrator of thepresent invention, it maybe desirable to provide a dehydrator arrangement affordingpassage'of the drying air eitherin alternately opposite directions or at difierent temperatures, humidity-and static pressures. Still other dehydrator arrangements may require a path of food travel of such length-that it is impractical to employ but a single .pair of screens I and 2 and associated air flow chambers 5 and Gas in-the. arrangement of Figure I.

.' In. suchcases, the dehydrator may comprise a plurality 'ofwdehydrator sections or units, each embodyingthe construction of'Figure 1 arranged in a' substantially verticalsuccession or series, for example, as shown-"in Figure 4 of thexdrawings. Inthis arrangement, comprising four vertically superimposed dehydrator sections or units of the type and construction previously described, it will be noted that the direction Of flow of'the drying medium through the column of food F, between each of-the respective pairs of chambers 5 and 6, 5a and 611, 51) and 6b, andl5c andtc, is*'in"alternately opposite directions and entirely separate and independent of the? other pairs-of chambers thereby making it possibleto employ'drying'air at different temperatures, humidity and/or pressure conditions in each' stage or s'ection ofthedehydrator. Of course, this] arrangement-of'Figure i is not limited to alter-j nately reversed air flow or todifierent temperatures, humidity orpressure conditions in the several stages and it should be understood that in all of the stagesthe direction of air fldwmay be the same "as well as maybe temperature, hu-' midity and'pressure conditions of the drying air. An important factorin multiple unit or cell arrangements, such as that of Figure 4, which must be taken into consideration, particularly in installations employing alternately opposite 'directionsof air flow, is the tendency existing in the region of the junctions between adjacent units or' sections for the input air, to follow the path ofleastresistance andbypass around the horizontal chamber division wall into the exhaust chamber immediately above 'or below instead of passing horizontally through the food column to theoppositely disposed or corresponding ex-' haust chamber. To minimize members or blocks I9' are disposed between the screens or plates of adjacent dehydrator units or sections, and thesesp'acers or blocks I9 have a, height'jor dimension vertically of the dehydra-" tor which isslightly in excess of the distance or spacing between the adjacentpairs of screens or plates of each section so that air entering, for

example, chamber 5, will tendto pass through the food F to the oppositely disposed corresponding chamber Brather than bypass about the end into the subjacent exhaust of .the partition 8 chamber 5a.

As in the case of the drier of Figure l,'in the multiple section arrangement shown in Figu'r'e4,

the several pairs of screens or plates I, 2 and so on, aremounted for adjustment relative'to each other in the manner previously described to vary,

as between each pair of "screens, the spacing thereof and/or their relative angular disposition to regulate and control the gradient or rate at which the width or thickness of the food column F increases as it progresses downwardly through the successive sections or units of the dehydrator. In this connection, it'is'pointed, out that ,the rateor angle of flare of the screens in the several'successive stages or sections of the dehydrator may or may not be thesame oruniform, and

while in Figure 4 thescreens are disposed to provide a uniform flare or rate of increase in the I spacing therebetween throughout the height of the dehydrator, it should b borne in mind that I the rate of increase of the spacing between the screens may be different, and vary, in the sev-" eral sections or stages depending upon the drying and flow properties of the particular food through the successive sections or stages of thedehydrator.

this, suitable imperforate spacer I ais zi oas dehydrators or drierscomprisingra series or succession of dehydrator sections-.onunits; forex-x amplaas in the arrangement shown rinrFigure 4i itrmay be necessary or desirable to provide, for access: 110115116, food at 011620). more points inthe course of passagethereoi through the; dehydrator for thepurpose ofuinspecting looseningor otherwise handling the food, and dehydrators .comprising such. aseries ofsectionsor units,gas afore aid, may be readily and easilyarranged topro vide. access to. the; food passing therethrough begtween adjacent or successive dehydrator or drier sections. 7 One such arrangement is shown in. Figure 91, the drawings wherein, the topmost g section or, unit. of the dehydrator ;,is. disposed. in laterally ofi'set relation. to the underlying sections. orunits. By this construction, it willbe observed that the food to be driedmay: be fedaconveyor to.the hopper 3 .from which it,.feeds. downwardly betweenthe screens or plates l and 2 of thetop section of. the dehydrator. and as the foodemerges from said top section itflows laterally anddownspondlng eexhaustschambersr- 6d and ElvandsofDIYthL' I lnil-ieu of theaparticulanair flow arrangement at Figures. 5 and. 6,; -it'. will; b obvious that the partition. or wall which'separates the twochamhers 5a and 5b 'may .be removedand the duct work. arranged so thatdrying: air entering chamber ihrfrom. chamber vlib may enter-the chamber Strand from this pass ina reverse direction through: the column of'foodl? to the chamber 6a. Qteourse, ine-such arrangement the air input to the chamber 5a, merely would be disconnected and, in'some cases, it will-be found advantageous to provide .asuitable heating device between the chambersia and 5b to reheat the drying air'from chamberfib .as it passesto the cham ber. 5a. a

wardly through an opening. orbreakAprovided' between the top section and. the next succeeding dehydratorsection and then is discharged into the inlet opening ofthe. second dehydratorsection through which it.fiows,-ultimately reaching. the final section .Irom which. it. dischargedin the dehydratedor dried condition desired. The. break'or opening A provided between the first. and second. drier sectionsas described; afi'ord's'a. point. of access to the ioodfor theinspection,

sampling, orin handling thereof, or..for removal" after partial. dehydrati'on for subsequent proc-. essing. v v I i As in the-case of the dehydrator'showninFigure 4,.the modified. construction= shown. in Figure may be arrangedsd that. the 'directionotfiow of. the. drying air. through the. recur! between each of the v res'pectivepairs ofchambers 5. an; 5a,.and 6a, and 5b and. 6b,. is in-.alternately o.pp o.-

site directions and. entirely separate and independentof the other pairs. of chambers there.-

try-making. it possible to employ" drying, air at P difierent temperature. humidity and. pressure 1 conditions. ineeach. stage or. section. of the .d'e'hy j drator, although .itis tube. .understood..'that "inv all of. the sections the. direction of; air. new and the temperature, humidity andpressure. condi 3 tionsof the air maybe the.same..

{Figure-6. of. thedrawings shows I hed'ehydrator oreigure 5. in..perspectiye.and-in association with.

one, suitable .arrangementaof..duots,.,.blowers. and r heaters .for. conditioning .and circulating the .dryg ing. air through the. food passing ,through the severaltsectionsor units of'the'dehydrator. or drier.

.1 Referring to saidFigure, 6; aduct 2f leadsirom.

theairjexhaust chamber eofthetop section; of. t 1 the. dehydratorthroughasuitableairheating. .de.-; ,vice'ii'v to .the suctionside or lintakeoiabloweri Z 3, from. which the heated air. is.di scharged 'under predeterminedstatic pressureethrough .a. duct 1 24.. to the input chamber 5' of. said. section. and;

, thence. through the food. E to saidpchamherffi v from whichitis exhaustedbythe.suctionoflthe blower; 23,..reh'eatedand thenmeciroulate'dfifrom. 1 the same. or. any ther. one. or ,n1ore,stagesL jsimilarly" in. the. 1 succeeding dehydrator: sec?- tioiis,.the air is. ei'rhausted :fromthe chambers ea.

and 5bwthrough ductsf25. and 26.by the fanil",

heated. by. the heating. devicegil. and-then. dis.-

charged under pressure by, said. fanll; through. 1. ducts2=9-and -;30. to theinput-chambersiirand 6b, respectively, and through the food F to the corre- In-certain dehydrator installations, and in particular those whereinwthe rateof. travel of the food. downwardly betweentthe screens is relatively rapid, it may be desirable to provide for control of the directionoi air flow as desired inv each v. dehydrator section or unit; This may beaccomplishedior example, .by a construction such as shown in-Figure 7 of. -the drawings, whereinairductsdl 'and. 32, each of which iscdmnionto bothof thelair chambers 5 and 6 at opposite. sides of the screens I and 2,,arearranged at. opposite ends of thedehydrator. and provided with. suitably arranged hinged bafiie members 33 and134} respectively, which may be positioned alternatively, as shown, to connect the ducts 3iand 3?.to one. or the other of the air chambers- 5 and16,..tliereby controlling thedirection of air.

passage through the. screens. and 2 and the material,therebetween' Too, if, desired, the

baffle members 33'] and 34 may. .bemechanically;

versaliof thedirecti'on of air flow as between corwherein theresistance to. passage of the air to provide a maximum. temperaturedrop is-efiected byincreasingthe length of the path. of airtravel through the material asdryingthereof progresses with. an accompanying decrease inIthe rate of moisture diffusion. 'Too,..the invention provides for control and regulation of thev length of :this pathof airtravel in accordance with the requirements of a particulardrying operation and the kind andtype of materialbeing. dried, andby' virtue oftheselective adjustability cfthe screen members of .each unit independently of other' units'it' is possible. to obtain a drying. operation of any desired character ml each stage or unit of 5' the dehydration. I

' Economically, the invention substantially elimi'riates the .necessityfor. expensive and space con-i sumin'g'; mechanically movable transporting de vices" such as conveyors, and the like, and" is of" comparatively inexpensive, relativelysimple con-1 structi'on, readily adaptable forus'e'in multiple arrangements' in parallel, or comprising a suc .cessionor seriesarrangement-and/or in laterally arranged-banks or groups;

whilecertain' embodiments ofthei-invention have been herein illustrated and described,'- it is not :intendedthat the invention be limited to" such: disclosure but that changes and modifications:-. :maya .be made and incorporated therein within the: scope of the claims: .Iclaim: Y

1. A dehydrator comprising; ambppbg i a rz 15. of .upright screen inwbers spacedzapartim; e

downwardly diverging relation with inner faces thereof defining therebetween a path for gravitational descent and gradual lateral spreading of. a bulk of loose separated material undergoing de- 7 hydration, vertical end walls cooperating with the upright marginal edges of said screens in defining said path cross sectionally, a chamber.

extending along the full length andbreadth of each screen adjacent the outer face thereof, means for building up gaseous fluid in the chamber at one side of said path to a pressure forcing said gaseous fluid transversely through -said bulk of material to the chamber at the oposite side of said path, the gradual increasing of the thickness of the bulk of material between said screens offering correspondingly increased resistance to the flow of fluid through the drier material in the lower part of said path in substantially equal ratio to the resistance offered by the wetter material in the upper part of said path to produce uniformity of said transverse flow of said gaseous fluid at all points throughout the length of said path, fluid pressure end passages connecting said screens to form said path, a chamber extending along the full length and breadth of eachscreen adjacent the outer face thereof, means for building up gaseous fluid in the chamber at one side of said path to a pressure forcing said gaseous fluid transversely through said bulk. of material to the chamber at the opposite side of said path, the gradual increasing of the thickness of the bulk of material between said screens offering correspondingly increased resistance to the flow of fluid throughthe drier material in the lower part. of said path in substantially equal' ratio to the resistance offered by the wetter material in the upper part of said path to produce uniformity of said transverse flow of said gaseous fluid at all points throughout the length of said path, fluid end passages connecting'said chambers around said end walls respectively, fluid inlet and outlet conduits connected to said end passages respec- ,tively, and fluid switchgates in said jend passages for directing fluid into and out of said chambers the path of one unit tothe path of the next adjacent unit.

- HIRAM W. WOODWARD. 

